Surface dose and PDD data were measured to determine the degree of radiological exposure in different organs in patients undergoing an X-ray examination. Through these of these data, the degree of radiological exposure to any particular organ in the body can be estimated. A survey of radiological conditions was conducted at a hospital in Okayama Prefecture to determine the degree of fetal exposure in pregnant women undergoing a plain abdominal X-ray examination. The results demonstrated that the degree of exposure varied greatly from one fetus to the next. Also, based on the mean radiological exposure, it was determined that 164 X-ray examinations would equal the threshold value of the biological tolerance of human fetuses.Furthermore, plain X-rays were taken from the lateral side of the lumbar region to investigate the effect of bone tissue on fetal exposure. The results revealed that the degree of radiological fetal exposure was affected by the presence of bone tissue, but this effect was negligibly detectable when a fetus was at least 10 cm away from the bone tissue.In terms of measures to reduce radiological exposure, shifts in PDD were analyzed by attaching an added filter to the outlet to increase total filtration. The results demonstrated that the degree of reduction in radiation dose for deep areas of the body was smaller than that for surface areas, and that the tendency was that the higher X-ray tube voltage or the thinner the filter, the smaller the rate of reduction.As the results, patient dose in radiological diagnosis was smaller than that in giving rise to the acute biological damages, but radiologists or radiological technologists must cooperate to minimize patient exposure in X-ray examinations.